Appraisal of active tectonics in Hindu Kush: Insights from DEM derived geomorphic indices and drainage analysis

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• 作者：Syed Amer Mahmood^a ; ^b ; ^{amerpakistan@gmail.com} ; Richard Gloaguen^a
• 关键词：Active tectonics ; Geomorphic indices ; IRAT (index of relative active tectonics) ; Hindu Kush ; Pakistan&ndash ; Afghanistan
• 刊名：Geoscience Frontiers
• 出版年：2012
• 期刊代码：pc98_16749871
• 类别：ear
• 出版时间：July, 2012
• 卷：3
• 期：4
• 页码：407-428
• 文件大小：11494 K

摘要

Landscapes in tectonically active Hindu Kush (NW Pakistan and NE Afghanistan) result from a complex integration of the effects of vertical and horizontal crustal block motions as well as erosion and deposition processes. Active tectonics in this region have greatly influenced the drainage system and geomorphic expressions. The study area is a junction of three important mountain ranges (Hindu Kush-Karakorum-Himalayas) and is thus an ideal natural laboratory to investigate the relative tectonic activity resulting from the India-Eurasia collision. We evaluate active tectonics using DEM derived drainage network and geomorphic indices hypsometric integral (HI), stream-length gradient (SL), fractal dimension (FD), basin asymmetry factor (AF), basin shape index (B_s), valley floor width to valley height ratio (Vf) and mountain front sinuosity (S_mf).

The results obtained from these indices were combined to yield an index of relative active tectonics (IRAT) using GIS. The average of the seven measured geomorphic indices was used to evaluate the distribution of relative tectonic activity in the study area. We defined four classes to define the degree of relative tectonic activity: class 1^__very high (1.0聽鈮ぢ營RAT聽<聽1.3); class 2^__high (1.3聽鈮ヂ營RAT聽<聽1.5); class 3鈥攎oderate (1.5聽鈮ヂ營RAT聽<聽1.8); and class 4鈥攍ow (1.8聽鈮ヂ營RAT). In view of the results, we conclude that this combined approach allows the identification of the highly deformed areas related to active tectonics. Landsat imagery and field observations also evidence the presence of active tectonics based on the deflected streams, deformed landforms, active mountain fronts and triangular facets. The indicative values of IRAT are consistent with the areas of known relative uplift rates, landforms and geology.